Conventionally, in a semiconductor device manufacturing process, a substrate such as a silicon wafer or a compound semiconductor wafer has been processed by supplying a processing liquid such as an etching liquid toward a central portion of the substrate from the above while rotating the substrate.
In some cases, the processing liquid such as an etching liquid may be heated to a predetermined temperature for efficiency of a substrate processing. However, after the processing liquid is heated to the predetermined temperature, the temperature of the processing liquid is decreased due to thermal conduction to the substrate until the processing liquid reaches an outer peripheral portion of the substrate after being supplied to the central portion of the substrate. That is, as being close to the outer peripheral portion of the substrate, the temperature of the processing liquid is decreased. As a result, there may be processing non-uniformity in processing caused by the processing liquid between at the central portion of the substrate and at the outer peripheral portion thereof.
In this regard, Patent Document 1 describes a technique of heating an outer peripheral portion of a substrate by supplying a high-temperature gas to the outer peripheral portion of the substrate. According to this technique, it is possible to suppress the temperature of the processing liquid from being decreased at the outer peripheral portion of the substrate by heating the outer peripheral portion of the substrate.
Patent Document 1: Japanese Patent Laid-open Publication No. 2011-054932
However, the technology described in Patent Document 1 needs to be further improved in order to optimize a heating processing on an outer peripheral portion of a substrate.
By way of example, there may be a case where a substrate is processed using an etching liquid heated to a predetermined temperature and rinsed with pure water and then, a substitution processing of substituting the pure water on the substrate with IPA (isopropyl alcohol) is performed. In such a series of substrate processings, if an outer peripheral portion of the substrate is continuously heated, volatilization of the IPA is promoted by heating, for example, during the substitution processing. Therefore, the pure water may not be sufficiently substituted with the IPA.
For this reason, the heating of the outer peripheral portion of the substrate, i.e., discharge of the high-temperature gas to the outer peripheral portion of the substrate, may be considered to be temporarily stopped. However, if the discharge of the high-temperature gas is stopped, when the discharge is restarted, it takes some time for a temperature of a gas to be discharged to reach the predetermined temperature. For this reason, it is necessary to wait for the starting of a next substrate processing with the etching liquid until a temperature of the gas reaches the predetermined temperature. Therefore, a throughput may be decreased.